Armor plate



Patented May 2t, 2940 ARMOR. PLATE Everett L. Reed, Arlington Heights, Mass.

No Drawing.

Application December 15, 1938,

Serial No. 245,927

4 (Claims.

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relatesto armor plate and to a method of treating it.

Light armor, 1 inches or less in thickness, is used to furnish protection against small arms bullets, intermediate caliber projectiles and shell fragments. It must possess the physical qualities of hardness, toughness, ductility and strength. Because of the incompatibility between hardness and toughness and between ductility and strength, the desired properties must be obtained by a proper selection of alloy steel and by suitable working, fabrication and treatment.

While it has been'common practice to faceharden heavy and medium armor plate by carburizing the difficulty of providing the requisite toughness and ductility in a very thin plate and the problem of securing the proper chemical compositions has established a preference for the homogeneous type for light armor although this type offers less resistance to penetration.

The purpose of this invention is to provide face-hardened light armor which will meet modem ballistic requirements and be capable of withstanding cumulative vibratory stresses produced by the impact of bullets from automatic weapons. A further purpose is to provide a process of treating light armor which will insure uniformity in the product.

The following examples of steel alloy for the composition of light armor plate forming the subject of this invention are as follows:

An addition of .20-.40 molybdenum may be added to the above to promote toughness.

The purpose of including the tungsten is to produce fine particles of uniformly distributed hard tungsten carbides in the carburized face, the function of which is to shatter bullets.

The heat treatment of the armor plates according to the invention consists of the following:

1. Normalizing 1 -2V hours, 940-970 C.

2. Annealing 2V -8l/ hours, 830-860 C.

3. Carburizing 48-55 hours, 900-950 C. in standard carburizing mixture, cooling in box.

4. Hardeningheat 22% hours at 850-875" C.-

water quench.

5. Tempering-reheat 2-2% hours at 200-225 C.,

air cool.

The above treatments cover armor plates inch in thickness. Before carburizing the plates are copper coated on the back face to prevent carbon penetration thereon.

Tests show that the plates have excellent ballistic resistance with no spalling under impact of a high velocity bullet. The high hardness of the face is effective in shattering the bullet core while the relatively soft body of the plate is effective in absorbing the energy of impact.

I claim:

1. As a new article of manufacture, light armor plate formed from a plate of alloy steel containing about 0.20 to 0.35 per cent of carbon, about 0.40 to 0.80 per cent of manganese, about 0.55 to 0.85 per cent of chromium, about 0.15 to 0.25 per cent of vanadium, about 2.5 to 3.5 per cent of tungsten and the remainder substantially all iron, said plate having its exposed surface carburized to form a bullet-shattering case having a fine distribution of tungsten-chromium carbide.

2. As a new article of manufacture, light armor plate formed 'from a plate of alloy steel containing about 0.20 to 0.35 per cent of carbon, about 0.40 to 0.80 per cent of manganese, about 0.55 to 0.85 per cent of chromium, about 0.15 to 0.25 per cent of vanadium, about 2.5 to 3.5 per cent of tungsten, about 0.20 to 0.40 per cent of molybdenum and the remainder substantially all iron, said plate having its exposed face carburized to form a bullet-shattering case having a fine distribution of tungsten-chromium carbide.

3. The process of heat treating light armor plate made from a steel alloy containing about 0.20 to 0.35 per cent of carbon, about 0.40 to 0.80 per cent of manganese, about 0.55 to 0.85 per cent of chromium, about 0.15 to 0.25 per cent of vanadium, about 2.5 to 3.5 per cent of tungsten and the remainder substantially all iron which comprises thesteps of normalizing for 1 to 2%; hours at 940 to 970 C., annealing 2 to 3 hours at 830 to 860 C., carburizing 48 to 55 hours at 900 to 950 C., hardening by heating 2 to 2 hours at 850 to 875 C., quenching in water at the latter heat, tempering by reheating 2 to 2 hours at 200 to 225 C., and air cooling.

4. The process of claim 3 applied to light armor plate having 0.20 to 0.40 per cent molybdenum added.

EVERETT L. REED. 

